How to ensure javascript addition instead of string concatenation (Not always adding integers)

问题

Through my javascript library, I end up with a string that represents a number. Now I want to preform an addition on that number without it doing a string concatenation instead. The solution is easy ( How do I add an integer value with javascript (jquery) to a value that's returning a string?, How to make an addition instead of a concatenation) if your number is always in integer. However my string could be a float or an integer, and at the time of the addition, and I don't know which it will be. Is there a way to make sure the addition happens regardless of whether it's a float or integer?

回答1:

Try using parseFloat. The input variables will be converted to floats, which will work whether the string contains an integer or a float. Your result will always be a float.

回答2:

It is reasonably safe to always use parseFloat even if you are given an integer. If you must use the appropriate conversion, you could match for a decimal point and use the appropriate function.

回答3:

I'm going to assume that float addition is sufficient, and if it isn't, then you'll need to dig deeper.

function alwaysAddAsNumbers(numberOne, numberTwo){
  var parseOne = parseFloat(numberOne),
      parseTwo = parseFloat(numberTwo);
  if (isNaN(parseOne)) parseOne = 0;
  if (isNaN(parseTwo)) parseTwo = 0;
  return parseOne + parseTwo;
}

To take what @Asad said, you might want to do this instead:

function alwaysAddAsNumbers(a, b){
  var m = 0,
      n = 0,
      d = /\./,
      f = parseFloat,
      i = parseInt,
      t = isNaN,
      r = 10;
  m = (d.test(a)) ? f(a) : i(a,r);
  n = (d.test(b)) ? f(b) : i(b,r);
  if (t(m)) m = 0;
  if (t(n)) n = 0;
  return m + n;
}

this will always give you at least a zero output, and doesn't tell you if either one is NaN.

回答4:

For some reason.... who knows???

Using parseFloat works.... when parseInt does not... obviously they are not always the same.

FWIW.... I'm "adding" data elements from "checked" checkboxes here...

    var AddOns = 0;

    $( '.broadcast-channels').each(function(){              
        if ( $(this).prop("checked")) {                             
            var thisAddOn =  parseFloat($(this).data('channel'));      
            AddOns = AddOns + thisAddOn;                                      
        }           
});

来源：https://stackoverflow.com/questions/12982128/how-to-ensure-javascript-addition-instead-of-string-concatenation-not-always-ad

标签

javascript

string

numbers

addition